A realtime monitoring system based on fiber Bragg grating sensing and photoelectric imaging technology is established to learn the deformation information of supporting structure in the process of foundation pit excavation. The measuring principle of the horizontal displacement and settlement of wall top by optical fiber grating measuring strain and photoelectric bidirectional displacement meter is introduced, and the formula of calculating horizontal displacement by measuring strain of fiber Bragg grating is derived. During foundation pit excavation, the comparison and analysis of the results of different displacement testing methods show that the fiber grating sensing technology is accurate and reliable for measuring the wall strain, and the horizontal displacement measured by the inclinometer coincides with the horizontal displacement measured by the inclinometer; the photoelectric bidirectional displacement meter is more accurate than the total station in terms of measuring horizontal displacement and settlement, which is worth popularizing.